Tanning of hides and skins



M. M. MERRITT TANNING-0F HIDES AND SKINS,

Aug. 9, 1938;

iwavraq kW M. M

Filed June 21, 1955 Patented Aug. 9, 1938 TANNING or nnms AND SKINS Matthew M. Merritt, Middleton, assignor .to The Tanning Process Company, Boston,

Mass., a corporation of Massachusetts Application June 21, 1935, Serial No. 27,733

7 Claims.

This invention relates to the tanning of hides and skins. While the invention will be described with reference to the chrome tanning of skins, it will be understood that the invention and various characteristics thereof may have other applications and uses.

In the chrome tanning of hides and skins, and in certain methods employed in the vegetable tanning of skins, it has heretofore been the prac- 10 tice to remove the hides or skins from the tanning drum or paddle at the end of the treatment by the tanning solution and then to horse up the hides or skins and allow them to stand from twentyfour to forty-eight hours to drain and to permit fixation of the tanning material with respect to the collagen fibers of the hide or skin substance. Alternatively, the hides or skins have been piled do'wn flat and allowed to drain from twenty-four to forty-eight hours during which the tanning material becomes set in the hide or skin substance. In either case, the hides or skins do not receive uniform treatment, it being obvious that those lower in the pile are under greater pressure than those at or near the top of the pile so that drainage must be very uneven. Furthermore, the hides .or skins at or near the top and the marginal portions of many of the hides or skins are exposed to the air and are thus dried-out more than hides or skins lower in the pile and more than those portions of the hides or skins which are entirely covered by hides or skins above them in the pile. This is a matter of considerable importance since the well-known tendency of tanning liquids to become uniformly diffused throughout hide or skin 5 substance is upset and even reversed where'the rate of drying of one part of the skin is substantially greater than in an adjacent portion. As a matter of fact, marginal portions of hides or skins which have dried too quickly are com- 40 monly hard even to the point of brittleness because of increased tanning material collected therein. Furthermore, if oxidation of the collagen constituent of the hide or skin takes place during or after the treatment by vegetable tanning material, as certain authorities contend, it would appear undesirable to expose certain skins or parts oi. skins to the air while other skins or parts of skins are covered, since under such conditions uniformity is apt to be lacking in the 50 finished leather.

It'is an object of applicants invention to provide for such treatment of the hides or skins at this period of tanning operations as will secure much more uniform distribution of the tanning 5 material in the hides or skins, and more uniformity in other respects, while the tanning material is being fixed in or upon the hide or skin fibers.

It is a further object of the invention to provide against uneven shrinkage in portions of the hides or skins as compared with other portions of the 5 same or other hides or skins, and to obtain a better product as a result of the tanning operation.

To these ends, and in accordance with an important characteristic of the invention, the hides or skins, at the completion of treatment by liquid 10 tanning material, are supported, individually in an atmosphere substantially saturated with moisture, for a period of, hours to secure uniformity in the distribution of tanning material throughout the hides or skins and its fixation with respect to 15 I the collagen fibers of the hide or skin substance. Since the hides or skins are individually supported there is no undue pressure of one hide or skin against another as in prior methods of treatment.

Furthermore, there is substantially uniform treat- 20 ment of the hides or skins from the standpoint of the moisture and temperature content of the surrounding air. In practice, each hide or skin is folded ,over its own supporting rod with the backbone portion thereof resting on said rod and sub- 25 stantially equal portions of the hide or skin depending from the rod on'each side thereof, the work pieces and rods being arranged in series side by side and one above another so that the depending portions of the hides and skins in each verti- 3o cal series are in overlapping contact with each other, but without pressing unduly upon each other in either lateral 'or vertical directions since the weight in each case is sustained by the individual rod, the whole series of hides or skins 35 being enclosed in a space having walls adapted to retain the moisture from the skins so that there is substantially no evaporation during the many hours that the hides or skins are allowed to undergo this treatment, during which equaliza- 4 tion and substantially complete fixation of the tanning substance takes place upon the hide or skin fibers.

The invention resides also in a cabinet or other enclosure, for treating hides and skins, having a 5 plurality of rods in both horizontal and vertical rows and disposed in the cabinet-so closely adjacent to each other in the vertical rows that hides or skins supported thereby will overlap each other from top to bottom of said vertical rows. In the illustrated construction, the rods are supported by brackets projecting from one or more walls of the cabinet and adapted to support a plurality of series of rods and the work pieces carried thereby in both vertical and lateral arrangement 5 whereby the cabinet may be packed or almost completely filled with hides or skins, the brackets being so closely spaced with respect to each other in the vertical direction that the hides or skins supported on the rods overlap each other from top to bottom of the cabinet in a plurality of series arranged side by side, each hide or skin thus having its own individual support, and the cabinet being substantially air-tight so that the hides or skins are maintained in a substantially uniform condition of temperature and humidity during the setting of the tanning substance upon the hide or skin fiber.

These and other features and characteristics of the invention will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawing,

Fig. 1 is a front view of a cabinet illustrating one embodiment of the invention, the doors of the cabinet being open to show skins in place therein;

Fig. 2 is a more or less diagrammatic view showing the disposition of the skins draped over supports located within the cabinet; and

Fig. 3 is a sectional view also taken along the line III III of Fig. 1, but without any skins in the cabinet.

In the illustrated embodiment of the invention, which is specially designed for the treatment of skins such as sheep-skins, there is shown a cabinet 4 which is a box-like structure haying door 6 hinged to side frames of the cabinet and constructed and arranged to close in such manner as to form a substantially air-tight box. Within the cabinet, and conveniently attached to end walls 8 of the cabinet, are brackets I arrangedin pairs, the brackets of each pair being in alinement with each other horizontally so as to support in the desired manner a plurality of rods or bars I2, the latter being adapted to support skins I4, as clearly shown in both Figs. 1 and 2. While rods I2 are shown as supported by brackets I0, it is clear that they may be supported in other ways.

In the method of supporting the skins shown in the drawing, each of the latter is draped over a rod or bar I2 in such manner that the backbone portion of the skin rests on the rod with approximately equal portions of the skin depending upon each side of the rod. Preferably, and as shown, the brackets III are positioned so closely to each other in the vertical direction that the skins in each vertical series or row overlap each other from top to bottom of the supporting brackets II]. It will be understood that in assembling the skins shown in Figs. 1 and 2 of the drawing, the operator begins at the bottom, placing a skin upon a rod and inserting it in place upon the lowest pair of brackets Ill and at the back of the cabinet. Then the next skin is placed upon a rod and put in position upon the next pair of brackets above the lowest pair, and these operations are continued until a vertical series or row of skins has been placed in the cabinet. Other rows or series of skins are introduced into the cabinet in a manner similar to that described until the cabinet is substantially filled with skins. Then the doors 6 are closed, thus retaining within the cabinet a relatively small body of air thoroughly saturated with moisture which has evaporated from the skins. The skins are allowed to remain in this moist atmosphere for a period which may be as long as two days, although commonly-chrome tanned skins will be found to be thoroughly tanned at the end of twenty-four hours. It is to be understood, however, that hides or skins which have been properly tanned may be kept in moist condition in this cabinet for a number of days, a week or more, without deleterious effect.

While the skins are shown draped over the rods I2, they may be secured to said rods or to other suitable equivalent supporting members by fastenings or by sharp pointed devices permanently secured to such supporting members or rods. With this method of supporting the skins, the latter will hang from one edge and will depend from one side of the supporting member or rod I2. In that case, the brackets I0 will normally be spaced somewhat further apart than those shown in the drawing. However, the skins in each vertical row or series will overlap each other from top to bottom of the cabinet.

Since the skins are normally quite wet with liquid tanning material when placed in the cabinet, it is desirable to have a container such as that shown at I6 in the bottom of the cabinet to receive any drippings from the skins.

It will be observed upon inspection of the drawing that the skins supported as described upon individual rods I2 do not press upon each other unduly. Hence, the tendency of the liquid tanning material to become distributed uniformly throughout the skin is not interfered with by pressure from other skins as it would be if the skins were piled flat or horsed up in a pack in accordance with commonly accepted methods. While there is some tendency, of course, for the liquid tanning material to collect in the relatively looser flanks and shanks of the skins this is not a drawback, it having been found by actual test that these parts are not overtanned as a result of this method of treatment in a moisture -retaining cabinet. On the contrary, they clearly appear to be tanned in a manner that is substantially uniform with the denser body portions of the skins. Due to the fact that the skins are maintained at ordinary room temperatures and in a moist condition throughout the period of treatment within the cabinet, there is ample time for the tanning material to distribute itself with substantial uniformity throughout the whole substance of the hide or skin. Experience has proven that this would not take place if some part of the hide or skin were allowed to dry to a sub stantial extent as compared with other adjacent portions of the same hide or skin. Furthermore, when these skins, after having received the described cabinet treatment, are subjected to a test such as that consisting in the well-known boiling test, theywill be found to be thoroughly tanned. This boiling test is founded upon the well-known fact that a piece of a row skin or of an imperfectly tanned skin will shrivel and be destroyed by boiling water, whereas a properly tanned piece of skin will stand the effect of boiling water for five minutes without apparent damage.

It is true that skins which have been allowed to dry following treatment by an adequate tanning preparation will become thoroughly tanned in the drying operation, without this preliminary treatment in a cabinet. But there is not the same uniformity in the tanning effect, it being quite common to find marginal portions of the skins overtanned, as shown by hardness and even brittleness of these parts. Furthermore, the dried skins must be wet back in order to continue finishing operations. On the contrary, the skins coming from the cabinet herein described are so CAlION OF TEXTILES & FIBERS,

"uniform in their tanned condition and in their moisture content that they take other finishing treatments, such as dyeing and fat liquoring, quickly and with uniformly good results.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of tanning skins which comprises removing skins from a tanning solution, where they have been subjected to treatment for the requisite length of time, draining the skins to remove such tanning liquid as flows freely therefrom, placing the skins upon individual supports, maintaining the air surrounding the skins substantially saturated with moisture at'ordinary room temperatures, and subjecting the skins to this moist air treatment for a period of about twenty-four hours to secure fixation of the tanning material on the skin substance.

2. That improvement in methods of tanning skins which comprises removing skins from a tanning solution, where they have been subjected to treatment for the requisite length of time, hanging the skins up individually in overlapping contact with each other in a row from top to bottom of a substantially air-tight enclosure, and adding to the row of skins thus formed other similarly formed rows until the enclosure is substantially filled with skins, whereby the skins are kept in an atmosphere substantially saturated with moisture.

3. That improvement in methods of tanning skins which comprises removing skins from a tanning solution, where they have been subjected to treatment for the requisite length of time, draining the skins to remove such tanning liquid as flows freely therefrom, and hanging the skins up in a substantially air-tight enclosure in a plurality of vertical rows in which the skins of each row overlap each other and in which the skins of successive rows are in contact with each other, whereby the tanning material becomes uniformly distributed in the skins and set on the fibres thereof while the skins are in an atmosphere saturated with moisture.

4. That improvement in methods of tanning skins which comprises removing skins from a tanning solution, where they have been subjected to treatment by a tanning solution for the requisite length of time, draining the skins to remove such tanning liquid as flows freely therefrom, hanging the skins, in a substantially airarch R00 tight enclosure, draped over rods or bars in vertical rows with the skins in each row overlapping each other from top to bottom of the substantially air-tight enclosure, and adding to the number of rows until the enclosure is substantially filled with skins, whereby all of the skins are allowed to become thoroughly and uniformly tanned while in an atmosphere saturated with moisture. I

5. A cabinet or other enclosure for treating freshly tanned hides or skins, while they are still wet with the tanning liquid, provided with a plurality of horizontal rods arranged in both horizontal and vertical rows and disposed in the cabinet so closely adjacent to each other in the vertical rows that hides or skins supported thereby will overlap each other from top to bottom of said vertical rows. 6. A cabinet or other enclosure for treating freshly tanned hides or skins, while they are still wet with the tanning liquid, provided with a plurality of brackets arranged in vertical rows in the cabinet, rods extending transversely of said brackets in a plurality of vertically disposed series of said rods, said brackets being so closely adjacent to each other in the vertical direction that the hides or skins supported by said rods are disposed in overlapping contact with each other from top to bottom of said brackets, and the cabinet being substantially air-tight to retain the moist condition of the hides or skins substantially unchanged during the period of treatment of the latter.

'7. A cabinet or other enclosure for treating freshly tanned hides or skins, while they are still wet with the tanning liquid, provided with a plurality of brackets extending from a wall of the cabinet in such closely spaced relation to each other in the vertical direction that hides or skins supported by said brackets will overlap each other from top to bottom of said brackets, a plurality of hide or skin carrying rods arranged side by side in such close relationship on said brackets that the cabinet may be substantially filled with hides or skins individually supported in overlapping relation in vertical planes and in contact with each other transversely of said vertical planes, the cabinet being substantially air-tight to retain the moisture in the hides or skins during all of the period of their treatment in said cabinet.

MA'I'I'HEW M. MERRII'I'. 

